Manganese-containing material treated by the invention can include manganese dioxide bearing batteries such as zinc-carbon, alkaline, and lithium (LMO or LiMn2O4) batteries, and manganese minerals, including ores, or nodules.
Polymetallic or manganese nodules from the seafloor are rock concretions formed of concentric layers of iron and manganese hydroxides around a core.
Seafloor manganese nodules include in their composition, at least Mn and usually Ni, Co, Cu, Zn, and Fe, with minor amounts of titanium, vanadium, molybdenum, and cerium. Often present in addition are one or more of the following metals: magnesium, aluminum, calcium, cadmium, potassium, sodium, zirconium, titanium, lead, phosphorus, and barium.
All of the desired valuable metals in manganese nodules are tied up with insoluble oxidized manganese, such as MnO2. Only about 9% of the manganese contained in the nodules is acid soluble. Thus it is necessary to reduce the MnO2 by a suitable reducing agent as a first step in order to recover the metal constituents. Historically, SO2 has been used for this purpose. However such prior art processes often do not recover a suitable manganese product and are capable of recovering only from about 80 to about 92% of the primary metal values, and often produce large quantities of waste. Lead is not soluble in sulfates or chlorides, thus reduction of compounds containing lead requires large sized equipment with the attendant high capital cost.